Add Worker pool and max concurrency setting

[symm]

No description provided.

[codecov]

Codecov Report

Merging #25 into master will increase coverage by 11.55%.
The diff coverage is 82.6%.

@@             Coverage Diff             @@
##           master      #25       +/-   ##
===========================================
+ Coverage   65.78%   77.34%   +11.55%     
===========================================
  Files           4        4               
  Lines         114      128       +14     
===========================================
+ Hits           75       99       +24     
+ Misses         37       27       -10     
  Partials        2        2

Impacted Files	Coverage Δ
main.go	0% <0%> (ø)	⬆️
vape.go	96.92% <100%> (+1.8%)	⬆️

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